Variable resistance



July 24, 1928. 1,677,886

E. c. BALLMAN VARIABLE RESISTANCE Filed Feb. 10, 1923 Fi 1 //7ve/7 mp.

' 5mm CBa/lman,

wire 2 is doubled and Patented July 24, 1928.

UNITED STATES PATENT i a nnwm c. Barman, or s'r. LOUIS, mrssouar, nssreuon TO vALnnY com-w rm, or am. LOUIS, mrssounr,

Vanuatu A conronnrron or nnnawm RESISTANCE.

Applicationllld February 10, 1923 Serial No. 618,259.

This invention relates to resistance units, and more particularly to adjustable resistance units arranged for convenient mounting on the apparatus with which the resistance is to be" used. v

One of the objects of this invention is to provide an. adjustable resistance unit which may be adjusted so as to vary the resistance adually and which may be fixed in its adustment at a desired oint.

. Another object of this invention is to provide a resistance unit' which shall be conveniently arranged for mounting.

Another object of this invention is to provide a unit which shall be compact in design and amply ventilated.

Further objects will appear from the detail description taken in connection with the accompanying drawing, in which:

Figure 1 is a'view in elevation of a resistance'embodying this invention;

gigure 2 is a bottom view of Figure 1; an

Figure 3 is a partial section on line 3-3, Figure 1.

In accordance with this invention the resistance conductorhas the form of a Wire usually of one of the so-called resistance materials. portin tube orbarrel 1 of insulating material. he surface of the barrel 1 may be grooved helically so as to provide a bed in which the wire may lie so as not only to revent its displacement from the support,

ut to insure auniform and permanent spacing of the successive turns. The. conductor has the looped end attached to a screw 301 other fastening device for fixing the end of the lzwire to the barrel. When the loop has been anchored to the screw, 3, the wire is thenwbund double so as to. lie in the helical coves;- on the barml. The barrel is woun full of wire, except for the space occupied by the supportin terminals at the bottom. 1'

e barrel 1 is itself'mounted upon a pair of metallic su porting terminals 4 and 5 extendin in pre erably opposite directions from the ottom of the barrel. minals are each provided with an up-turned lip or flange 6 bent so as to conform to the outer surface of the barrel and attached spring-lock-washers as mdicated' in Figure rations 11, onl

These perforatmns are placed adjacent a This wire is coiled upon a sup- These ter-- 2 so as to prevent their working loose.-' The terminals 4 and 5' provide a pair of outwardly extending wings equipped with notches 9 and 10 for engaging the terminals upon which the resistance unit is to be mounted. These notches are turned in 'different directions at right "angles to each other so that they may be engaged with a pair of terminals having a fixed spacing in a manner. well known in the art.

The barrel 1 is provided at diametrically opposite points near the bottom with erfoone of which is s own.

pair of opposite screws 8 and the'ends of the resistance conductor wire are passed through these perforations to the inside of the barrel when the wire has beenicomplet'elywound thereon. After passing to the interior. of

the barrel, the ends are'secured under the spring-washers of thescrews. 8. One end of the resistance conductor wire is thus connected to each of theterminals 4. and 5 so that current may -be ledinto and out'ofthe resistance by means of theseterminals.

I Mounted on the barrel 1. and surrounding the same is a'circular metallic collar 12,.the ends 13 of which are turned up as illustrated forations '14 may be passed. A nut 15 may be soldered to the collar 12 and'the corresponding up-turned lip 13 may be engaged by the screw 14 for clamping the collar on the barrel. The collar 12 is provided at spaced points with indentations 16 adapted to pro vide inwardly projecting knobs or buttons.

in Figure 2 to form lips provided with perthrough which a clamping screw.

The collar 12 is placed upon the barrel in such a way that each of these buttons comes between a pair of adjacent turns of the conductor 2. Since the conductor is wound so that the turns project somewhat from the surface of the barrel, the collar will be retained in position by the these buttons with the wire. At the'same time each button forms a metallic bridge be tween adjacent turns of wire so as to short circuit apair of turns. It will be evident that by loosening collar may be turned on the barrel so as to cause a button 16 to slide along between the adjacent wires. Since the wires are in the form of a screw thread, rotation of the collar 12 will gradually feed the same along the barrel in one direction or another acengagement of cheapening the construction.

cording to the direction of rotation, the col-" lar being guided by engagement of thebuttons 16 with the wires 2. Thus a very grad u al adjustment of resistance is obtained,

since by moving the short circuiting button 16 along the wlre as described, a greater or less extent of wire may be included in the circuit between the terminals 4 and 5'. The resistance can thus be gradually adjusted to any desired value within its range and when.

and cheaply'constructed of molded insulation or other suitable insulating material. If molded insulation is used the groove can be molded therein simultaneously, thereby The doubly wound resistance wire provides a practicall non-inductive resistance. The adjustable c0 lar 12 being adjustable by means of the screw thread-action described above provides f a very gradual and accurate adjustment of the resistance and the clamping feature provides for permanently setting the resistance at the desired adjustment. The hollow barrel construction provides for easy ventilaout.

It is obvious that various changes maybe made in details of construction without departing from the spirit of this invention; it is, therefore, to be understood that this invention is not to be limited to the specific details shown and described.

Having thus described the invention, what is claimed is:

1. An electrical resistance unit comprising ductor wound in said roove a movable contact collar surrounding said barrel and punched to rovide a plurality of rounded interior pro ections spaced one from the other and adapted to contact with adjacent turns of said conductor and be guided thereby, and means for clamping said collar in adusted position.

3. An electrical resistance unit comprising a helically grooved barrel, a resistance conductor wound in said groove, a movable contact collar surrounding said barrel and punched to provide a plurality of rounded interior projections spaced one from the other and adapted to contact with'adjacent turns of said conductor and be guided thereby, and clamping means for said collar adapted to shorten the circumference thereof.

4. ing a helically grooved barrel, a resistance conductor wound in said groove and a movable contact collar surrounding said barrel and having spaced rounded interior projections adapted to contact with adjacent turns of said conductor and be guided thereby, and supports for said barrel adapted to provide terminals for said conductor.

In testimony whereof I aflix my signature this-28th day of December, 1922.

EDWIN O. BALLMAN.

An electrical resistance unit compris' 

